1. Technical Field
The present invention relates to a valve assembly which is attached to a gas cylinder containing compressed gas or liquefied gas for the use of taking out the gas and charging it, and to a pressure reducing valve provided in the valve assembly. More specifically, it relates to a valve assembly adapted so as to be able to take out a high pressure gas contained in a gas cylinder through an outlet bore while being reduced by the pressure reducing valve at the time of gas taking-out and charge the high pressure gas into the gas cylinder through the outlet bore at the time of gas charging.
2. Description of the Earlier Technology
A pressure reducing valve provided in a gas cylinder valve assembly of this kind has a piston member inserted into a pressure reducing valve chamber within a housing, the piston member being adapted so as to move for opening and closing by a balance between a spring force for valve opening and a secondary (valve-outlet) pressure for valve closing.
By the way, a housing for the valve assembly has to be made compact in accordance with the size of a gas cylinder. Therefore, conventionally, superposed coned disc springs are adapted so as to apply the spring force for valve opening in order that a pressure reducing valve to be provided within the housing can be made compact. The structure of superposed coned disc springs has, in its height direction, one end received by the housing and the other end received by the piston member (for example, Japanese Patent Public Disclosure No. 3-219172).
However, a coned disc spring has a spring constant far larger than that of an coil spring. Therefore, if the coned disc spring is mounted at a height changing due to variation of errors caused when manufacturing the pressure reducing valve chamber and the piston member, the spring force largely changes to result in widely fluctuating a set value of the secondary pressure as well.
In order to keep the secondary pressure within a set range, conventionally it was required to absorb the variation of manufacturing errors by attaching a height adjusting shim at an end of the coned disc spring or exchanging the piston member or the like parts. This took time and labor in assembling the valve assembly.